Ethane standard enthalpy

Example Calculate the standard enthalpy change for the oxidation of ethanol (C2H5OH) to ethanal (CH3CHO), given the following standard enthalpies of combustion ... 

Consider the estimation of the standard enthalpy of formation of gaseous ethane, Af/7"(C2Hb, g) (known to be —84.667 kJ moU )- The target reaction is ... 

Ethane is flamed off in abundance firom oil wells because it is unreactive and difficult to use commercially. But would it make a good fuel The standard enthalpy of reaction for 2 CjHdCg) + 7 02(g) —>... 

C02(g) + 6 H20(1) is -3120 kJ. (a) What is the standard enthalpy of combustion of ethane (b) What is the specific enthalpy of combustion of ethane (c) Is ethane a more or less efficient fuel than methane ... 

CI2 is the most spontaneous, I2 is the least. Spontaneity is determined by the standard enthalpy of formation of the dihalogenated ethane. Higher temperatures make the reactions less spontaneous. 

Calculate the standard enthalpy change of formation of ethane, CjHg. 

Let us apply equation (7.22) to calculate the standard enthalpy of combustion of ethane, C2Hg(g), a component... 

These values of A Hr are standard state enthalpies of reaction (aU gases in ideal-gas states) evaluated at 1 atm and 298 K. 7VU values of A are in kilojoules per mole of the first species in the equation. When A Hr is negative, the reaction hberates heat, and we say it is exothermic, while, when A Hr is positive, the reaction absorbs heat, and we say it is endothermic. Tks Table 2-2 indicates, some reactions such as isomerizations do not absorb or liberate much heat, while dehydrogenation reactions are fairly endothermic and oxidation reactions are fairly exothermic. Note, for example, that combustion or total oxidation of ethane is highly exothermic, while partial oxidation of methane to synthesis gas (CO + H2) or ethylene (C2H4) are only slightly exothermic. 

Table 7.3 The C-C bond energy of ethane by HF, MP2(fc), and DFT (B3LYP, M06, and TPSS) calculations, at 0 and 298 K. The basis set is 6-31G. Standard, tabulated bond energies are for dissociation at 298 K. Bond energy = 2(CH3 radical enthalpy) - (CH3CH3 enthalpy). For the radical the unrestricted method (UHF etc.) was used. For the 0 K dissociation enthalpy, the HF and MP2 calculations use energies corrected for ZPE, with the ZPE itself corrected by a factor of 0.9135 (HF) or 0.9670 (MP2) [77]. The 0 K dissociation enthalpy for the DFT calculations is uncorrected for ZPE, and the 298 K dissociation enthalpy is from standard statistical thermodynamics methods [79]. The experimental C-C energy of ethane has been reported as 90.1 0.1 kcal mol-1, i.e. 377 0.4 kJ mol-1 [80]. Calculations are by the author...

Temperatures of over 700 °C are necessary to favor ethene formation over ethane formation. Propene/propane and isobutene/isobutane show similar behavior, although the lower reaction enthalpies of propane and isobutane dehydrogenation (124 and llSkJ mol, respectively, at standard conditions) versus ethane dehydrogenation (137 kj mol ) favor the unsaturated form of longer... 

Thermodynamics disfavors the dissociation of CO2 to O2 and CO in the gas phase. Under standard conditions, the enthalpy of dissociation is A H° = +293.0 kJ/mol. At 427°C, the dissociation constant Kp is only about 10 . The literature shows that CO2 could play an oxidant role, but only at high temperatures (usually > 650°C). In fact, the first applications reported on the use of CO2 were those working at very high temperature reactions such as methane oxidative coupUng and ethane oxidative dehydrogenation. However, Dury et al. reported recently that, in the presence of oxide and noble metal catalysts, CO2 can dissociate and act as an oxidant at much lower temperatures (below 450°C). ... 

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